1. Field of the Invention
This invention pertains to tractors generally, and in particular, to walk-behind hand tractors also known as mono-axle or two wheel tractors.
2. Description of the Background
Walk-behind hand tractors, including hand tractors with multiple attachments for performing various grounds maintenance chores have been commercially available in the marketplace for a long time. An example of this can be found in E. L. Rose (U.S. Pat. No. 2,538,708). At present, hand tractors of this type employ a single transmission, either gear or hydrostatically driven, coupled through a differential to the drive wheels. In this current design, the operator makes directional changes to the tractor by applying body weight force to the handles. Still others have steering brakes that effectively brake the inside wheel causing the tractor to turn toward the braked wheel. Unfortunately, the effect of the differential drive is to transfer all the motion to the unbraked wheel thereby doubling its wheel speed and making the tractor difficult to control. The differential drive also makes the tractor unstable and hard to control on sloped terrain. As the tractor navigates across the slope, the operator must use body weight force to counter the tractor's tendency to turn downhill. This can lead to operator fatigue and a loss of traction and control of the hand tractor. A further disadvantage of this design is that motive power is biased to the wheel with the least grip. This is a particular disadvantage when the tractor is attempting to perform chores where maximum traction is necessary like mowing slopes or moving snow. A still further disadvantage is that the brake components are subject to premature wear and constant maintenance and service.
Still other tractors in the prior art utilize wheel drive with a hydrostatic pump-to-motor transmission. This configuration affords the operator the ability, through valving, to effectively slow down or stop the inside wheel to cause a turn. These hand tractors, while a substantial improvement to the differential design, have certain drawbacks as well. This design does not enable the operator of the tractor to make the wheels rotate in opposing directions to cause a zero radius turn. Furthermore, these hand tractors have proven to be complicated and expensive to build and have yielded only limited success in the marketplace.
Still other embodiments exist in the prior art such as Wenzel (U.S. Pat. No. 5,127,215) and Walker (U.S. Pat. No. 7,146,787). These machines effectively deploy independent dual drive motion control to the drive wheels enabling the operator to perform a zero radius turn. These machines have vertical crankshaft motors that utilize a belt configuration in the horizontal plane that connects directly to the lawn mower, or in the case of Walker, to a series of complicated and expensive gearboxes and drive shafts to power the mowing unit. These machines, while functional for lawn mowing, serve little purpose, if any, in utilizing other chore performing attachments.
To be complete, it must be mentioned that nowhere in the prior art does there exist, to applicant's knowledge, a hand tractor that utilizes an attachment adapting method with integral power take off (PTO), that can be deployed quickly, easily and safely, by one person without disabling the hand tractor.
The need exists in the marketplace for a reliable, simply designed, walk-behind hand tractor with independent control to each drive wheel that has the ability to be operated with one hand and that can rapidly and safely deploy attachments by a single operator without tools. To date, to applicant's knowledge, no such hand tractor has been available in the industry.